SSL SiX - Routing ideas / Audio Interface

Hear some great suggestions in this thread. Just a quick question.

My goal is to run a stereo signal through ALT 1/2 inputs

Do I need to hard pan alt 1/2 to left/right for stereo use? …or should those inputs be automatically switching to “stereo mode” when both input lines are connected?

I just want to check that my unit is functioning normally